Silver bromid gelatin and process of making same.



NITED STATES PATENT OFFICE.

ALBERT OOBENZL, OF BINGEN, GERMANY.

SILVER BROMID GELATIN AND PROCESS OF MAKING SAME.

SPECIFICATION forming part of Letters Patent. No. 718,312, dated January13, 1903. Application filed June so, 1902. Serial No. 113,842. (Nospecimens.)

T0 at whom, it may concern:

Be it known that I, ALBERT CoBENZL,a subject of the Emperor ofAustria-Hungary, residing at Bingen-on-the-Rhine, Germany, have inventedcertain new and useful Improve-- ments in Silver Bromid Gelatin andProcesses of Making the Same; and I do hereby declare the following tobe a full, clear, and exact description of the invention, such as will.enable others skilled in the art to which it appertains to make and usethe same.

In order to make a sensitive silver bromid gelatin which does not cloud,it has often been proposed to add alcohol during the emulsification orto precipitate it with alcohol. As, however, by this procedure thesilver bromid gelatin is always precipitated in larger or smaller lumpsor is chilled into a stiff condition and must in order to be washed bemade finer, the washing operation is naturally inconvenient, and byreason of irregular reduction in size of particles the gelatin isinsufficiently and imperfectly washed, especially when the washingoperation is not done with great care and for a sufficient time. Thesilver bromid gelatin so obtained does not always exhibit the desiredqualities. According to the herein-described process all thesedifficulties are avoided and a product is always without failureobtained in an easilywashable form, which product possesses an evendegree of sensitiveness and all desirable qualities.

According to this invention this result is attained by preparing anemulsion liquid with alcohol or similar substances in such a manner thatthe gelatin or the like at the temperature necessary to its preparationremains in a perfectly clear solution. After maturing or ripening of theemulsion it is cooled to about 13 to 14 centigrade-say 52 to 57Fahrenheitwith simultaneously stirring briskly, so that the silverbromid gelatin is separated as a heavy sandy powder. As the thusobtained powder precipitates rapidly, it can readily be separated fromthe clear solution containing the soluble salts and easily and perfectlyobtained in a pure state by washing. An emulsion thus obtained has,further, the advantages that with equal sensitiveness compared with theemulsions prepared by the present employed processes it has a much finergrain. It is sensitive to a greater range of the prismatic colors,especially green, orange, and redthat is, the emulsion preparedaccording to the herein-described process has especially goodpanchromatic qualities. The two above-named properties, to which are duea finer-grained silver bromid gelatin, are es-' pecially valuable inmicrophotography, astronomy, and projection.

An example of one manner of carrying out the process is here given. Onehundred and fifty grams of gelatin or the like are swelled in twothousand five hundred cubic centimeters of water, then fully dissolvedtherein by heating, and to the thus obtained solution there are addedsix hundred cubic centimeters of the following solutions: two hundredand ninety grams of calcium bromid, one thousand five hundred cubiccentimeters of ninety to ninety-five per cent. alcohol, and six hundredcubic centimeters of the following solution: two hundred and twentygrams of silver nitrate, three hundred cubic centimeters of water, sixhundred cubic centimeters of ninety to ninety-five per cent. alcohol.This mixture is allowed to ripen or mature at from 60 to 80 centigrade,or, say, 140 to 176 Fahrenheit, for about from one to three hours,according to the degree of sensitiveness desired, and is then rapidlycooled by vigorous stirring. At a temperature of about 12 to 14centigrade, or, say, 54 to 57 Fahrenheit, the silver bromid gelatinprecipitates as a fine sandy powder and can be fully separated andobtained in a pure state by decanting, filtering or the like, andwashing.

The addition of the usually-employed substances, as bromid salts, (also,if desired, a1- kaline carbonates,) renders the emulsion readyforflowing on plates, paper, &c. The silver bromid gelatin thus preparedis afinegrained powder that swells in cold water, but does not dissolvetherein; is, however, soluble in warm water. It is insoluble in alcohol,ether, or beuzol. A specially characteristic property of this silverbromid gelatin and of the herein-described process is that the gela tin,while possessing the same sensitiveness as those made by other methods,has an essentially finer grain and is sensitive to a greater range ofthe spectral colors, so that itis nearly absolutely panchromatic.

Having now particularly described my invention, what I claim, and desireto secure by Letters Patent, is-

1. A process for the manufacture of silver bromid gelatin, whichconsists in subjecting the solution of the emulsion in a hot state totheaction of alcohol, then allowingit to ripen, then cooling it byagitation so that the silver bromid gelatin precipitates from the clearliquid which contains the soluble salts, as a fine-grained sandy powder,and then separat ing the same and washing.

2. Silver bromid gelatin consisting of a precipitated powder with a veryfine grain being nearly panchromatic.

In testimony that I claim the foregoing as my invention I have signed myname in presence of two subscribing witnesses.

ALBERT OOBENZL. [L. S.]

Witnesses:

EDWARD MIES, WALTER HANSING.

